The invention relates to a double seat valve, in particular for gas safety equipment, comprising a valve body with an upper valve disk and a lower valve disk, an upper valve seat for the upper valve disk and a lower valve seat disposed underneath for the lower valve disk, and an adjustment element for the valve body for opening this valve body against the action of a closing spring.
Gas slide valves with a flat slide as closing element are known for closing off pipes, which flat slide is slid in front of a bore from the side until the pipe is tightly sealed off. However, these flat slides are slid further in front of the bore by a certain overtravel than is necessary for closing off the pipe. Although the gas slide valves are not any tighter due to this overtravel, the perception developed that gas slide valves are particularly tight because they are closed further by the overtravel. A proof-of-closure switch is only activated after sealing and the overtravel by the slide.
Such gas slide valves are mainly used for manually closing off a gas pipe and to a lesser extent for controlling and adjusting the gas supply. A gas slide valve, driven mostly by a motor via a screw, opens and closes far too slowly for guaranteeing a fast safety shut-off of modern automatic gas-fired furnaces.
For valves with a valve disk, which seals when reaching the valve seat, and which cannot perform a further travel, the design as overtravel valve is very expensive and the basic idea of being safer can only be partly realized.
In FIG. 3 a known valve 100 with a first main valve disk 101 and an advancing second valve disk 102 is shown. However, with this valve disk 102 designed as rubber disk, which should improve the safety of the valve, the danger is that it prevents the main valve disk 101 from closing. Also, the rubber disk can tear due to wear and rest on the valve seat 103, which prevents closing. An elastically bearing advancing valve disk can tilt and thus again prevent the main valve disk from closing. The closing of the main valve disk can also be prevented if the advancing valve disk blocks a proof-of-closure switch.
It is hence the object of the invention to further develop a double seat valve of the above-mentioned type into an overtravel valve.
This object is solved according to the invention in that the valve body is guided displaceably on the adjustment element and that on the adjustment element a limit stop is provided which takes along the valve body in opening direction, which is spaced from its bearing, effective in taking along, on the valve body when the valve body is closed.
The advantage obtained with the invention is that the adjustment element first performs an idle stroke during opening, before the valve body is taken along. Upon closing the adjustment element makes an additional overtravel corresponding to the idle stroke, when the valve body already lies with its two valve disks on the respective valve seats.
In particularly preferred embodiments of the invention the adjustment element is displaceable into its bearing, effective in taking along, on the valve body against the action of a readjusting spring. Thus it is ensured that the adjustment element always performs the additional overtravel, also when the valve body has been closed. The closing spring of the double seat valve force-biasing the valve body in its closed position is designed such that a closing of the double seat valve is also ensured if the readjusting spring has been compressed. Thus the closing spring has an unequally greater force than the readjusting spring, which only serves for readjusting the adjustment element. The readjusting spring can be supported on the housing, or, which is preferred, between the valve body and the adjustment element.
The limit stop taking along the valve body can, for example, be a snap ring which is inserted into a snap ring groove of the adjustment element.
In order to minimize the friction between the valve body and the adjustment element, the adjustment element can be provided with a slide bearing for the valve body. Preferably the adjustment element is a magnetic armature with an armature tappet, on which the valve body is guided.
In preferred embodiments of the invention a proof-of-closure switch is provided, which can be activated by the adjustment element, which proof-of-closure switch switches only into its xe2x80x9cclosexe2x80x9d position after the double seat valve is closed, and into its xe2x80x9copenxe2x80x9d position still before the double seat valve opens.
The invention also concerns an arrangement with at least two double seat valves, as they are described above, in a common housing. In such an arrangement the double seat valve on the input side as well as the double seat valve on the output side are then equipped with an overtravel.